Book Description

-Conjugated polymers are promising active materials on account of their properties, which include electronic conductivity, electroluminescence and light-harvesting. Post-functionalization of conjugated polymers is a facile approach towards tailed structures and properties of polymers. This thesis reports on the synthesis and characterization of post-functionalized conjugated polymers and control phase segregation in donor-acceptor blends by post-functionalization of conjugated polymers for photovoltaic applications A graft copolymer, poly(3-hexlthiophene) bearing poly(vinyltriazole) (P3HT-g-PVTAZ), was used as the primary model material to demonstrate a novel strategy for controlling the size, contiguous nature, and extent of phase segregation of donor and acceptor domains. The graft copolymer was obtained by nitroxide-mediated radical polymerization of a vinyl triazole onto a postfunctionalized poly(3-hexylthiophene) (P3HT) backbone. The graft copolymer was blended with a fullerene modified with a similar motif - a pendant triazole functionality (TAZC60). TEM analysis revealed that the graft polymer undergoes extensive mixing with the fullerene to form bicontinuous 10 nm phase domains. Graft polymer blends annealed for 1 h at 140 °C retain their nanometer phase separation and domain purity was enhanced. The chemical similarity of the triazole functionality attached to P3HT and the fullerene leads to the formation of films with uniform, stable, nanophase morphologies. Synthesis of a perylene-functionalized conjugated polymer was used to demonstrate the templated growth of 1-D assemblies of perylene diimides (PDI) formed within a conjugated polymer. The strategy is demonstrated with poly(3- hexylthiophene) (P3HT), partially functionalized at the 4-position with N-(1- hexylheptyl)-N'-(12-carboxylicdodecyl)perylene-3,4,9,10-tetracarboxylbisimide (PP3HT). The 1-D assemblies of PDI embedded in the optoelectronically active polymer are hundreds of nanometers wide, 10 - 20 nm thick, several microns in length, and run parallel to the surface of the substrate. Surrounding the 1-D structures is a heterogeneous PP3HT-PDI blend. These systems represent structures of multiple hierarchy, wherein nano-sized domains of a -conjugated polymer and an n-type material are in intimate contact and which encapsulate 1-D assemblies of nanocrystallites that run parallel to the films surface. They offer an alternative route for the fabrication of innovative supramolecular structures for optoelectronic applications.